The present invention pertains to high voltage insulators, of the type use on high voltage power transmission lines, and more specifically to devices intended to be used on ends of such insulators, to reduce or eliminate corrosion and erosion effects associated with current leakage and corona discharge effects.
It is well known in the high voltage insulator art that insulator end fittings are prone to erosion and corrosion effects associated directly or indirectly with high voltage current effects, particularly in the case of insulators having non-ceramic bodies. Such effects are typically caused by ultraviolet radiation created by corona discharges from surfaces under high electric field stress; and also by leakage currents flowing across the insulator surface and terminating on end fittings.
These corrosion and erosion effects eventually can cause increasing weakness of the insulator strength member, and can eventfully result in a mechanical and/or electrical failure of the insulator, thus materially shortening the useful insulator life, as compared with the life it would have absent such effects.
There is thus a need for a device which can effectively prevent such corona discharges so as to eliminate the ultraviolet radiation, and also terminate the surface leakage currents in a manner which eliminates insulator corrosion and erosion.
As detailed below, the present invention accomplishes these objectives by an insulator terminator having the combination of a semiconductor element, of the form of a disk with rounded edges, and a surface conductive element, covering about half of the semiconductor element, which elements together shield the portion of the insulator near the insulator end fitting from high electric field stress, and also eliminate surface leakage current from the part of the insulator near the insulator end fitting, by shunting such current flow through the semiconductor element and surface conductor element of the present invention device, directly to the end fitting of the insulator, which end fitting connects to the power cable, at the lower end of the insulator, and to the tower or pole structure at the upper end from whence it is connected electrically to ground potential.